a) Field of the Invention
The present invention relates to a wiper for use in a vehicle for wiping a windshield glass or the like.
b) Description of the Related Art
In a wiper for use in a vehicle for wiping the wind shield glass or the like, it is necessary to set the angle of a wiper blade with respect to the windshield glass (i.e. attack angle) to be within a predetermined range over the entire wiping range (the wiping angle) so that, even if the windshield glass has a large curvature, the wiper can reliably wipe the glass without deterioration of its performance.
Accordingly, in order to meet the demand posed by windshield glasses of larger curvature, a wiper has been devised (for example, Japanese Utility Model Application Laid-Open No. 63-189858), in which a wiper arm is fixed and a pivot shaft for reciprocatively rotating the wiper arm is first disposed on the vehicle body so as to be inclined relative thereto, alternatively wiper (for example, Japanese Utility Model Application Laid-Open No. 63-189857), in which the direction of inclination of the pivot shaft relative to the vehicle body is changed by rotating the bearing and inner bearing of the pivot shaft independently of the shaft.
In this kind of wiper, (for example, in the wiper shown in Japanese Utility Model Application Laid-Open No. 63-189857), a bearing (termed an eccentric shaft in the above-described Utility Model) is disposed so as to rotate relative to the vehicle body about own axis, and so as to rotatably support the pivot shaft in an inclined position relative to the axis of the bearing. In addition, the pivot shaft and the bearing are each coupled to a wiper motor as a driving source via a linkage or the like.
When the wiper is actuated, the rotating force of the wiper motor is transmitted to the pivot shaft via the link or the like to cause the pivot shaft to reciprocatively rotate the wiper arm and blade, while at the same time the rotating force of the motor is also transmitted to the bearing so as to cause it to rotate independently of the pivot shaft.
As a result, the inclination of the pivot shaft relative to the vehicle body is changed according to the rotation of the wiper arm and blade and, even with a windshield glass of large curvature, the attack angle becomes easy to set within a predetermined range.
However, in such a conventional wiper, although the direction of inclination the pivot shaft relative to the vehicle body can be changed, it has not been sufficiently easy to adjust it when the attack angle is set within a predetermined range.
That is, the above-described bearing is reciprocated twice for a single reciprocating motion of the pivot shaft (wiper arm and blade). In other words, since the bearing is rotated at the beginning in the same direction as the rotating direction of the pivot shaft and is then inverted so as to be rotated in the opposite direction, in the substantially intermediate portion of the wiping range comprising the wiping angle of the wiper arm and blade, the resulting relative rotational directions of the pivot shaft and the bearing are opposite to one another, and, further, after the inversion, the relative rotational speed of both the pivot shaft and the bearing is doubled. In consequence, a change in the direction of inclination of the pivot shaft relative to the vehicle body, which is determined by the position at which the pivot shaft and the bearing are relatively rotated, becomes complicated, which makes it difficult to adjust the attack angle to within the predetermined range.
In addition, according to a conventional wiper, since a reduction gear mechanism is provided at the wiper motor portion and each reduction gear is individually coupled to the pivot shaft portion by means of a linkage so as to individually transmit the rotational force of each of the reduction gear, the entire system becomes bulky, which makes it difficult to dispose these parts and mechanism in a small space.